Comparative analysis of phytochemicals in different plant organs of <i>Verbascum thapsus</i> L. by using UPLC/MS-QToF and analytical standardization of bioactive compounds, verbascoside and luteolin, on HPLC platform

<i>Verbascum thapsus</i> L., commonly called Mullein, is widely used in Ayurveda for the treatment of numerous ailments. The major objective of the present study is to analyse the phytochemical composition of different plant organs of <i>V. thapsus</i>. UPLC/MS-QToF analysis of methanol extracts from different plant organs (inflorescence, leaf, stem, and root) of <i>V. thapsus</i> displayed 61 active biomarkers. Among those, 48 compounds were found in the inflorescence, 40 in the leaf, 32 in the stem, and 29 in the root of <i>V. thapsus</i>. The distribution of these compounds was further evaluated statistically using Venn and Heat map diagrams. Moreover, a novel reverse-phase HPLC method was developed and validated as per ICH Q2(R1) guidelines to quantify verbascoside and luteolin of <i>V. thapsus</i>. The method was found suitable, specific, linear (<i>R</i>² > 0.999), precise, accurate, and robust. The current study's novel findings can help with the identification and quality control of verbascoside and luteolin in plant species used in Ayurvedic medicines.